25 U.S. Code § 139 - Appropriations for subsistence
The Secretary of the Interior, under the direction of the President, may use any surplus that may remain in any of the appropriations for the purchase of subsistence for the several Indian tribes, to an amount not exceeding $25,000 in the aggregate, to supply any subsistence deficiency that may occur:
For transfer of functions of other officers, employees, and agencies of Department of the Interior, with certain exceptions, to Secretary of the Interior, with power to delegate, see Reorg. Plan No. 3 of 1950, §§ 1, 2, eff. May 24, 1950, 15 F.R. 3174,64 Stat. 1262, set out in the Appendix to Title 5, Government Organization and Employees.